1. Field of the Invention
The present invention relates to a wet or dry wiping sheet for use in cleaning, disinfecting or sterilizing flush toilets, wiping the backside of humans, or cleaning rooms or for use as wet towel; more specifically, the present invention relates to a wiping sheet with expansions and fine wrinkles formed on the surface to thereby impart good wiping capacity to the sheet and with high strength; and a method for producing the same.
2. Description of the Prior Art
Wet sheets have been used for cleaning toilets or other rooms or have been used as a wet towel. These wet sheets consist of paper from wood pulp fiber or nonwoven fabric from absorbent fiber impregnated with cleansing fluid chemicals. The cleansing fluid chemicals include for example surfactants, cleansing components, preservatives, and fragrance in water and alcohol. As the wet sheets for cleaning flush toilets, use has been made of water-dispersion sheets (water-dispersion paper) impregnated with a fluid chemical suppressing the water dispersion.
Some of such wiping sheets are prepared so bulky to impart bulky touch to hands by laminating and bonding a plurality of sheets. As means for partially bonding between a plurality of sheets, adhesives are used in some of them. Particularly in wet sheets which can be flushed in flush toilets, water-dispersion sheets are bonded together with a water-soluble adhesive.
However, the wet sheets in prior arts are poor in bulkiness and very thin. When these wet sheets are used for wiping work being held by hands, no firm touch can be felt, so that the wet sheets may be readily slipped off through hands. Therefore, such wet sheets cannot impart good touch for use.
Furthermore, wet sheets with a flat surface disadvantageously cannot wipe off stain sufficiently from cleaning areas. Particularly, against the uneven floor with protrusions and recesses, the flat wet sheets hardly wipe off stain in the recesses.
A process of coating an adhesive on the surface of sheet made of paper or nonwoven fabric is required for bonding a plurality of sheets together with the adhesive. At the process of coating an adhesive, it is relatively easy to uniformly coat the adhesive on a given area of the surface of the sheet. However, if those sheets are bonded together through adhesives coated on a wide area, the resulting sheet is wholly stiff with poor softness to give unpleasant touch for hands in holding the sheet, because the ratio of the adhesive bonding area to the whole sheet area increases. Also, if the adhesive bonding area is too large, the wiping effect of stain may be deteriorated.
So as to bond together such sheets with an adhesive, therefore, an adhesive should be coated at intervals on the sheet surface, following a given pattern; and by subsequently using an emboss matching the coating pattern of the adhesive, preferably, the area coated with the adhesive is pressurized to form adhesive-bonding areas. The sheets, partially bonded together at intervals, may have sufficient softness and adequate ratio of the adhesive-bonding area to the whole sheet area, so that the wiping effect on the sheet surface can be enhanced.
In Japanese Patent Application No. 8-257032, the inventors of the present invention have proposed a bulky wiping sheet, which consists of a plurality of sheets with different crepe ratios to be bonded together through partial bonding areas. Being impregnated with a fluid chemical, each sheet extends in its own ratio of the elongation due to the crepe restoration, so that the expansions may be formed between the bonding areas. In this case, so as to regularly generate expansions on the sheet surface, it should be required to form the bonding areas at intervals.
The resulting wiping sheet with expansions is so bulky that the wiping sheet can be readily handled by hands, and wiping effect of stain may be excellent due to the expansions formed on the sheet surface.
However, with only the expansions formed between the sheet bonding areas, sufficient wiping effect cannot be expected against the uneven area having extremely fine protrusions and recesses.
Still more, so as to coat an adhesive at intervals following a given pattern on the sheet surface, a specific process such as screen printing is required. In this case, furthermore, the adhesive coating pattern on the sheet surface should be positioned to match the position of a pressure emboss of an emboss roll to pressurize the sheets. Thus, the arrangement and adjustment of the equipment for the work are then very laborious.
A conventional method for producing such sheets having high crepe ratios comprises;
a process of forming a web (base) from fiber such as pulp; PA1 a process of dehydrating the web under pressure by means of a press roll; PA1 a process of drying the web wound around a dryer with a heating roll; and PA1 a process of crepe-processing by applying a doctor blade onto the surface of the dryer and winding the web by means of a winding roll at a lead-in rate slower than the lead-out rate by means of the dryer. PA1 a first drying process of drying a sheet by means of the first heating roll to such an extent that water might remain in the sheet, the sheet containing an absorbent fiber produced by paper machine; PA1 a process of crepe-processing the sheet containing water by applying a blade to the first heating roll, while transferring the sheet at a lead-out rate by means of the first heating roll faster than the lead-in rate by means of a second heating roll; PA1 a second drying process of further drying the sheet by means of the second heating roll after being crepe-processed; PA1 a bonding process of partially bonding at least one first sheet produced at the aforementioned process to a second sheet with a crepe ratio lower than that of the first sheet or without any crepe, at a plurality of bonding parts; and PA1 a process of generating large wrinkles on the first sheet between said bonding parts, due to crepe restoration by impregnating with a liquid, whereby small wrinkles as residual crepe wrinkles are left on the first sheet. PA1 a process of coating an adhesive on the sheet face to form band-shaped regions which extend in parallel with the lead-out direction of the sheet; and PA1 a pressurizing process of overlaying another sheet onto the sheet face coated with the adhesive and partially pressurizing the sheets along said band-shaped regions at a given pitch so as to bond the sheets together within the pressurized regions to form said bonding parts.
According to said method, the sheet made from paper machine is dried completely or to an extremely low water content, by means of the dryer. Because the crepe is formed by applying means of the doctor blade after being dried in said manner, the resulting crepe-processed sheet may have extremely low strength or much powdery paper may be generated during the crepe-processing. This may possibly be due to the reduction of the bonding strength of the hydrogen bonds between the fibers because extraneous force from the doctor blade is loaded onto the sheet after dried.
Thus, if said bulky wiping sheet is prepared by using the sheets with a high crepe ratio produced by said conventional method, it would be extremely deteriorated in the sheet strength and be readily broken during wiping work. Still more, the powdery paper would be attached onto the surface of the wiping sheet, disadvantageously falling therefrom during wiping work.